Override property types in child classes in java android

Question

I'm trying to implement my app with the MVP (Model-View-Presenter) pattern in Android but I'm facing a problem. I want to have an abstract base presenter with a view class property that is of a generic type ViewInterface but when creating a real presenter I'd like this property to be of the type RealPresenterView and if possible without needing to override the same function in all presenters.

As I probably didn't explain myself properly here's a bit of code to illustrate the case, first the base presenter:

abstract public class BasePresenter {
    protected ViewInterface view;

    protected ViewInterface getView() {
        return view;
    }
}

then the real presenter

public class RealPresenter {
    protected RealPresenterView view;

    // ...
    view.methodOnlyExistingInRealPresenterView();
}

I wanted to be able to use the view in RealPresenter as RealPresenterView without needing to add much code in the class. Is that possible?

I've read about class templates but I haven't seen how to implement in this case without adding functions in every presenter.

Answer 1

You can use generics :

BasePresenter

abstract public class BasePresenter<T extends ViewInterface> {
    protected T view;

    protected T getView() {
        return view;
    }
}

RealPresenter

public class RealPresenter extends BasePresenter<RealPresenterView> {

}

Note that I didn't code in java for some time, but I think that's ok.